Add basic observability example to classic dataset (#3697)

* Add basic observability example to classic dataset

* Add boilerplate and observability schema

* Lint fix

* Add observability schema to project-factory module

* Extend duplicate-diff

* Fix tests

* Remove unused schemas

modules/project/logging-metrics.tf

@@ -1,5 +1,5 @@
 /**
- * Copyright 2025 Google LLC
+ * Copyright 2026 Google LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -71,7 +71,7 @@ resource "google_logging_metric" "metrics" {
   disabled    = each.value.disabled
   bucket_name = try(
     # first try to check the context
-    var.context.log_buckets[each.value.bucket_name],
+    local.ctx.log_buckets[each.value.bucket_name],
     # if nothing else, use the provided channel as is
     each.value.bucket_name
   )